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I'm confused then. I have eliminated my understeer by keeping my front tires at the maximum door jamb pressure (32) and the rears in the towards the low/middle side of pressure.

I don't have understeer...mine it pretty neutral right now. When I apply gas lightly through turns, I push out the rear end and definitely notice throttle steering.

You might increase the throttle steering response with higher pressure, but a little more pressure does make the tire diameter greater, and thus the same angle of steering causes more turning.

This is what I've read in many places and have direct experience with...just saying.

Mango, I agree, though, that I bet a lot of time has to do with contact patch and that using door jamb, even at autoX might be better than 40 all around (though that might be closer to your recommended pressures than mine). I'm 29-32 in front and 33-41 in rear (I think).

You said to increase the rear tire pressure to reduce understeer...and I'd said just the opposite. I wonder if AutoX is that different from 'regular' driving...because in DD, increasing the front tire pressure relative to the rear increases oversteer. For the same degree of turn in the tires, with more air, the tire is bigger, and thus more turning is done.

Are the physics in AutoX that different? I'm confused...or you just made a typo.

The tire has a range of pressure in which it will obtain optimal grip. Under-inflate the tire and it will roll over on the sidewall too much, decreasing grip. Over-inflate the tire and you will balloon out the center slightly, decreasing grip.

Because of this, there is no blanket statement that will *always* be true, as the balance between the front and rear are relative to one another. But in a situation like Mango described, where he's running 40PSI, running slightly higher in the rear will move the car's tendency more towards oversteer. If his pressures were lower (say 30 PSI), the same might not be true.

Every tire is different. But from my experience, when you're at the high end of your optimal range of pressures like that, running higher in the rear will loosen the back end up. I do this in my E36 on tighter courses where I want to steer more with my right foot. I run star specs, which have a very stiff sidewall and squared shoulder. Other tires would take more pressure to slide off in grip on the top end. But regardless, 40 cold is on the high side.

I'm confused then. I have eliminated my understeer by keeping my front tires at the maximum door jamb pressure (32) and the rears in the towards the low/middle side of pressure.

I don't have understeer...mine it pretty neutral right now. When I apply gas lightly through turns, I push out the rear end and definitely notice throttle steering.

You might increase the throttle steering response with higher pressure, but a little more pressure does make the tire diameter greater, and thus the same angle of steering causes more turning.

This is what I've read in many places and have direct experience with...just saying.

Mango, I agree, though, that I bet a lot of time has to do with contact patch and that using door jamb, even at autoX might be better than 40 all around (though that might be closer to your recommended pressures than mine). I'm 29-32 in front and 33-41 in rear (I think).

doug i'm going to have to complete disagree with you here. you haven't eliminated your understeer. tire pressure alone will not eliminate understeer. you will need to dial in several other modifications to get your car neutral. it's very hard to do.
also the pressures on the door jambs are NOT recommended for autocross. when you're cornering under extreme conditions your tire gets much more force than under street driving. you cannot drive as hard on the street as you do in autocross. i don't care who you are and where you drive you just can't do it.
in his original pictures you can see the tire tread patch. then you can see slight wear on the outsides of that. that is a sign the tire did not have enough pressure to deal with the force it had on it and needs to be increased. the tire will flatten the more weight you put on it and the sides will start to "roll over"
he should be running at least 40 psi. at my autocross yesterday i ran about 41 all around and still had slight rubbing outside of the tread patch. anywhere outside of that tread patch is considered to have zero grip.

Sometimes I've seen tape on the headlights, never known the reason for that.

I always just assume because racecar.

taping headlights for open wheel racing may be required at certain tracks because it is a way to protect the track from glass in the event of a collision.
during autocross there is no point.
also taping your car during autocross is kinda dumb unless you have r compound tires that literally pick up little rocks and throw them at your car.

I really like that you put your car to the test, mango. It gives me faith to push my further to it's limits, and I kinda' did that today. I know I have repairs to do, but you know us and our constant need for an adrenaline rush. Today, I decided to push the car a bit harder. They're were a couple of bends and curves, and I pulled out of em' with the rear sliding just a tad bit. It felt good! Only because I've never experienced the amazing control the 330 offers when it's pushed hard. Then I saw your post and smiled, haha. I'll be buying front/rear strut bars and front/rear h&r sway bars to improve the handling. I love the way the power train puts it's power down, but I don't think BMW's are street brawlers-in the drag racer sense. I think these cars shine in the track/autocross.

good advice, nick, although i know the basics of understeer, oversteer, lift throttle oversteer, weight transfer, etc. i do plan on knocking my pins next time before my next alignment. and yes im positive its my wheel bearings.

i did let my car idle after runs for about a minute. still great tips.

and dmax, afaik, raising front tire pressure relative to the rear will introduce even more understeer. it wasnt that bad.

good advice, nick, although i know the basics of understeer, oversteer, lift throttle oversteer, weight transfer, etc. i do plan on knocking my pins next time before my next alignment. and yes im positive its my wheel bearings.

i did let my car idle after runs for about a minute. still great tips.

and dmax, afaik, raising front tire pressure relative to the rear will introduce even more understeer. it wasnt that bad.

Sent from my SGH-T989 using Bimmer App

please speak more of your wheel bearing.
in my front left i had a humming for a few days. now it sounds like, what can only be described as, a dry bearing noise that is only present when moving. i also have a ever so faint clunk/click at random bumps.

I did OK considering it was my first time?. Miatas on sticky race tires were doing 38s. My fastest was 41.5 and i consistently did about 43 flat.

california speedway fontana. $80 ($75 sign up early)

Having raced Miatas for years, I can say that they can corner to the point of making your neck sore (no kidding)! Their light weight is easy on even the stickiest of race tires too, which is a bonus. Mazda actually made a coupe version as a test (genuine roof, not just a drop on hard top). I cant imagine how much better that car would have cornered with the additional structural stiffness. But they decided very few people would want a Miata with a permenant roof, other than racers, which was probably the right call.
Too bad the Z3 member matched their level of performance. That was a major lost opportunity on BMW's part. It is strange how two cars that look so similar on paper could end up so different.
Sorry, but I still have a soft spot for Miatas! If they had made a NA version with a small V6 and about 100 more HP, I probably would never have bought a BMW.

I really like that you put your car to the test, mango. It gives me faith to push my further to it's limits, and I kinda' did that today. I know I have repairs to do, but you know us and our constant need for an adrenaline rush. Today, I decided to push the car a bit harder. They're were a couple of bends and curves, and I pulled out of em' with the rear sliding just a tad bit. It felt good! Only because I've never experienced the amazing control the 330 offers when it's pushed hard. Then I saw your post and smiled, haha. I'll be buying front/rear strut bars and front/rear h&r sway bars to improve the handling. I love the way the power train puts it's power down, but I don't think BMW's are street brawlers-in the drag racer sense. I think these cars shine in the track/autocross.

I keep trying to convince my friends that this would be 10 times more fun than hammering on the gas pedal and running 12s/13s at the dragstrip. Not many people seem to be as excited at the thought of auto-x as myself..which is unfortunate.

Drag racing is boring unless you have more HP than you can use on the streets, IMO.
Now, if you have tons of HP, then it can be fun and/or scary. Some people have the impression that it just involves flooring it, which is pretty much true with cars with normal amounts of HP. But, if you ever get to drive a car with obscene amounts of HP, then it becomes something completely different. Tiny corrections can upset the car, and put you in to a cycle of back and forth corrections.

But Autocross is way more fun, and more within the reach of the average guy, and you are not risking a $10-20k engine when you do it.

good advice, nick, although i know the basics of understeer, oversteer, lift throttle oversteer, weight transfer, etc. i do plan on knocking my pins next time before my next alignment. and yes im positive its my wheel bearings.

i did let my car idle after runs for about a minute. still great tips.

and dmax, afaik, raising front tire pressure relative to the rear will introduce even more understeer. it wasnt that bad.

Sent from my SGH-T989 using Bimmer App

Didn't mean to insult your intelligence.

Sorry to hear about the wheel bearings. I hope it's the fronts, for your sake, if you DIY them.

Getting some more camber up front will make a noticeable difference. Depending on how much you squeeze out of it from knocking the pins out, you may want to dial the toe back a little to save the tires some wear.

Sorry to hear about the wheel bearings. I hope it's the fronts, for your sake, if you DIY them.

Getting some more camber up front will make a noticeable difference. Depending on how much you squeeze out of it from knocking the pins out, you may want to dial the toe back a little to save the tires some wear.

Nah no harm done Right, i'm currently toe in -.10 all the way around (since I do highway driving) but i might set dial it down or zero it out next time. I believe knocking the pins out is good for half a degree of camber (according to tis)

I'm ordering all four corners for the wheel bearings. Including all new hardware; axle nuts, dust caps inner and outer, snap rings

Having raced Miatas for years, I can say that they can corner to the point of making your neck sore (no kidding)! Their light weight is easy on even the stickiest of race tires too, which is a bonus. Mazda actually made a coupe version as a test (genuine roof, not just a drop on hard top). I cant imagine how much better that car would have cornered with the additional structural stiffness. But they decided very few people would want a Miata with a permenant roof, other than racers, which was probably the right call.
Too bad the Z3 member matched their level of performance. That was a major lost opportunity on BMW's part. It is strange how two cars that look so similar on paper could end up so different.
Sorry, but I still have a soft spot for Miatas! If they had made a NA version with a small V6 and about 100 more HP, I probably would never have bought a BMW.

Yeah I kind of thought of the idea of wanting to get one... but then it would have to be exclusively a track toy and it seems everyone at autocross has them for the sake of getting fast lap times--the same times as everyone else. It was funny, every single miata got the exact same time every time. Makes me wonder if they're just too easy to drive fast due to being so small and light? Not challenging???

Nah no harm done Right, i'm currently toe in -.10 all the way around (since I do highway driving) but i might set dial it down or zero it out next time. I believe knocking the pins out is good for half a degree of camber (according to tis)

I'm ordering all four corners for the wheel bearings. Including all new hardware; axle nuts, dust caps inner and outer, snap rings

Yeah I kind of thought of the idea of wanting to get one... but then it would have to be exclusively a track toy and it seems everyone at autocross has them for the sake of getting fast lap times--the same times as everyone else. It was funny, every single miata got the exact same time every time. Makes me wonder if they're just too easy to drive fast due to being so small and light? Not challenging???

They're very maneuverable. But with such a short wheel base, they can be less stable and more finicky to drive than something like a 3 series. It all depends on how they're set up though. I see some Miata guys swapping ends any time they make a mistake. You have to almost be trying to loose control of a BMW out there.

I keep up with most of the NA Miata's. Some of the FI ones are real fast though. There are a few at my local club that are pushing out some nice power. They're lighter, smaller, more maneuverable, and faster than a 3-series. There's just no way to match their times. Though, the satisfaction of having a refined, pleasurable daily driver like a 330i, that's also very capable out there without any modifications whatsoever...that's worth its weight in gold, IMO. It's all about enjoying the car and learning. There will always be someone faster. Having fun and improving as a driver is

Good luck with the bearings.
They're very maneuverable. But with such a short wheel base, they can be less stable and more finicky to drive than something like a 3 series. It all depends on how they're set up though. I see some Miata guys swapping ends any time they make a mistake. You have to almost be trying to loose control of a BMW out there.

I keep up with most of the NA Miata's. Some of the FI ones are real fast though. There are a few at my local club that are pushing out some nice power. They're lighter, smaller, more maneuverable, and faster than a 3-series. There's just no way to match their times. Though, the satisfaction of having a refined, pleasurable daily driver like a 330i, that's also very capable out there without any modifications whatsoever...that's worth its weight in gold, IMO. It's all about enjoying the car and learning. There will always be someone faster. Having fun and improving as a driver is

Very true. I didn't let the faster guys bother me at all. I enjoyed just learning my car. And I agree the 330 was very hard to lose control of... it was very stable.

Quote:

Originally Posted by choxor

I demand gopro footage of future mango autocross action (MAA).

I agree man. I wanted one bad that day. I would do 5D Mark II footage but need a sturdy mount first

I'm confused then. I have eliminated my understeer by keeping my front tires at the maximum door jamb pressure (32) and the rears in the towards the low/middle side of pressure.

I don't have understeer...mine it pretty neutral right now. When I apply gas lightly through turns, I push out the rear end and definitely notice throttle steering.

You might increase the throttle steering response with higher pressure, but a little more pressure does make the tire diameter greater, and thus the same angle of steering causes more turning.

This is what I've read in many places and have direct experience with...just saying.

Mango, I agree, though, that I bet a lot of time has to do with contact patch and that using door jamb, even at autoX might be better than 40 all around (though that might be closer to your recommended pressures than mine). I'm 29-32 in front and 33-41 in rear (I think).